Vertical solid-state transducers and high voltage solid-state transducers having buried contacts and associated systems and methods

ABSTRACT

Solid-state transducers (“SSTs”) and vertical high voltage SSTs having buried contacts are disclosed herein. An SST die in accordance with a particular embodiment can include a transducer structure having a first semiconductor material at a first side of the transducer structure, and a second semiconductor material at a second side of the transducer structure. The SST can further include a plurality of first contacts at the first side and electrically coupled to the first semiconductor material, and a plurality of second contacts extending from the first side to the second semiconductor material and electrically coupled to the second semiconductor material. An interconnect can be formed between at least one first contact and one second contact. The interconnects can be covered with a plurality of package materials.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/132,546, filed Dec. 23, 2020; which is a continuation of U.S.application Ser. No. 16/669,785, filed Oct. 31, 2019, now U.S. Pat. No.10,879,444; which is a continuation of U.S. application Ser. No.16/167,280, filed Oct. 22, 2018, now U.S. Pat. No. 10,475,976; which isa continuation of U.S. application Ser. No. 15/658,202, filed Jul. 24,2017, now U.S. Pat. No. 10,134,969; which is a continuation of U.S.application Ser. No. 15/019,748, filed Feb. 9, 2016, now U.S. Pat. No.9,728,696; which is a continuation of U.S. application Ser. No.14/850,715, filed Sep. 10, 2015, now U.S. Pat. No. 9,293,639; which is adivisional of U.S. application Ser. No. 14/607,839, filed Jan. 28, 2015,now U.S. Pat. No. 9,159,896; which is a divisional of U.S. applicationSer. No. 13/708,526, filed Dec. 7, 2012, now U.S. Pat. No. 8,963,121;each of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present technology is related to high voltage solid-statetransducers and methods of manufacturing solid-state transducers andhigh voltage solid-state transducer dies. In particular, the presenttechnology relates to vertical high voltage solid-state transducershaving buried contacts and associated systems and methods.

BACKGROUND

Solid state lighting (“SSL”) devices are designed to use light emittingdiodes (“LEDs”), organic light emitting diodes (“OLEDs”), and/or polymerlight emitting diodes (“PLEDs”) as sources of illumination, rather thanelectrical filaments, plasma, or gas. Solid-state devices, such as LEDs,convert electrical energy to light by applying a bias across oppositelydoped materials to generate light from an intervening active region ofsemiconductor material. SSL devices are incorporated into a wide varietyof products and applications including common consumer electronicdevices. For example, mobile phones, personal digital assistants(“PDAs”), digital cameras, MP3 players, and other portable electronicdevices utilize SSL devices for backlighting. Additionally, SSL devicesare also used for traffic lighting, signage, indoor lighting, outdoorlighting, and other types of general illumination.

Microelectronic device manufactures are developing more sophisticateddevices in smaller sizes while requiring higher light output with betterperformances. To meet current design criteria, LEDs are fabricated withdecreasing footprints, slimmer profiles and are subsequently seriallycoupled in high voltage arrays. In certain embodiments, the individualSSL dies may include more than one LED junction coupled in series.

FIG. 1A is a cross-sectional view of a conventional high voltage SSLdevice 10 a shown with two junctions in series in a lateralconfiguration. As shown in FIG. 1A, the high voltage SSL device 10 aincludes a substrate 20 carrying a plurality of LED structures 11(identified individually as first and second LED structures 11 a, 11 b)that are electrically isolated from one another by an insulatingmaterial 12. Each LED structure 11 a, 11 b has an active region 14,e.g., containing gallium nitride/indium gallium nitride (GaN/InGaN)multiple quantum wells (“MQWs”), positioned between P-type GaN 15 andN-type GaN 16 doped materials. The high voltage SSL device 10 a alsoincludes a first contact 17 on the P-type GaN 15 and a second contact 19on the N-type GaN 16 in a lateral configuration. The individual SSLstructures 11 a, 11 b are separated by a notch 22 through which aportion of the N-type GaN 16 is exposed. An interconnect 24 electricallyconnects the two adjacent SSL structures 11 a, 11 b through the notch22. In operation, electrical power is provided to the SSL device 10 viathe contacts 17, 19, causing the active region 14 to emit light.

FIG. 1B is a cross-sectional view of another conventional LED device 10b in which the first and second contacts 17 and 19 are opposite eachother, e.g., in a vertical rather than lateral configuration. Duringformation of the LED device 10 b, a growth substrate (not shown),similar to the substrate 20 shown in FIG. 1A, initially carries anN-type GaN 15, an active region 14 and a P-type GaN 16. The firstcontact 17 is disposed on the P-type GaN 16, and a carrier 21 isattached to the first contact 17. The substrate is removed, allowing thesecond contact 19 to be disposed on the N-type GaN 15. The structure isthen inverted to produce the orientation shown in FIG. 1B. In the LEDdevice 10 b, the first contact 17 typically includes a reflective andconductive material (e.g., silver or aluminum) to direct light towardthe N-type GaN 15. A converter material 23 and an encapsulant 25 canthen be positioned over one another on the LED structure 11. Inoperation, the LED structure 11 can emit a first emission (e.g., bluelight) that stimulates the converter material 23 (e.g., phosphor) toemit a second emission (e.g., yellow light). The combination of thefirst and second emissions can generate a desired color of light (e.g.,white light).

The vertical LED device 10 b typically has higher efficiency thanlateral LED device configurations. Higher efficiency can be the resultof enhanced current spreading, light extraction and thermal properties,for example. However, despite improved thermal properties, the LEDdevice 10 b still produces a significant amount of heat that can causedelamination between various structures or regions and/or cause otherdamage to the packaged device. Additionally, as shown in FIG. 1B, thevertical LED device 10 b requires access to both sides of the die toform electrical connections with the first and second contacts 17 and19, and typically includes at least one wire bond coupled to the secondcontact 19, which can increase a device footprint and complexity offabrication. Some of the conventional LED die processing steps have beenrestricted to the package level (e.g., after singulation at a die level(FIG. 1B)) to achieve high performance and prevent damage to the devicesduring processing steps. Such package-level processing steps increasedemands on manufacturing resources such as time and costs as well as canhave other undesirable results such as surface roughening of thepackage. Accordingly, there remains a need for vertical LEDs, verticalhigh voltage LED dies and other solid-state devices that facilitatepackaging and have improved performance and reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present disclosure can be better understood withreference to the following drawings. The components in the drawings arenot necessarily to scale. Instead, emphasis is placed on illustratingclearly the principles of the present disclosure. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIGS. 1A and 1B are schematic cross-sectional diagrams of LED devicesconfigured in accordance with the prior art.

FIGS. 2A-2L are schematic plan and cross-sectional views illustratingportions of a process for forming solid-state transducers in accordancewith embodiments of the present technology.

FIGS. 3A and 3B are cross-sectional views illustrating further portionsof a process for forming solid-state transducers in accordance withfurther embodiments of the present technology.

FIGS. 4A-4C are schematic plan views illustrating portions of a processfor forming a wafer level assembly having a plurality of solid-statetransducers configured in accordance with another embodiment of thepresent technology.

DETAILED DESCRIPTION

Specific details of several embodiments of solid-state transducers(“SSTs”) and associated systems and methods are described below. Theterm “SST” generally refers to solid-state devices that include asemiconductor material as the active medium to convert electrical energyinto electromagnetic radiation in the visible, ultraviolet, infrared,and/or other spectra. For example, SSTs include solid-state lightemitters (e.g., LEDs, laser diodes, etc.) and/or other sources ofemission other than electrical filaments, plasmas, or gases. SSTs canalternately include solid-state devices that convert electromagneticradiation into electricity. Additionally, depending upon the context inwhich it is used, the term “substrate” can refer to a wafer-levelsubstrate or to a singulated device-level substrate. A person skilled inthe relevant art will also understand that the technology may haveadditional embodiments, and that the technology may be practiced withoutseveral of the details of the embodiments described below with referenceto FIGS. 2A-4C.

FIGS. 2A-4C are schematic plan and cross-sectional views illustrating aprocess for forming SSTs in accordance with an embodiment of the presenttechnology. FIGS. 2A-2L illustrate various portions of the processshowing a single SST die 200 for clarity; however, it is understood thatthe illustrated steps can be implemented at the wafer-level forproducing a plurality of SST dies 200 concurrently using the processsteps described herein. For example, FIGS. 2A and 2B illustrate an SSTdie 200 at a stage of the process after a transducer structure 202 hasbeen formed on a growth substrate 220. As shown in FIG. 2B, the SST die200 has a first side 201 a and a second side 201 b facing away from thefirst side 201 a. Referring to FIGS. 2A and 2B together, the SST die 200can include a plurality of features that separate the transducerstructure 202 into a plurality of junctions 203 (identified individuallyas junctions 203 a-203 i). For example, trenches 208 that extend fromthe first side 201 a of the SST die 200 through the transducer structure202 to the substrate 220 can be formed to separate and electricallyisolate the individual junctions 203 from adjacent or other junctions203 on the SST die 200.

The transducer structure 202 can include a first semiconductor material210 at the first side 201 a, a second semiconductor material 212 at thesecond side 201 b, and an active region 214 located between the firstand second semiconductor materials 210, 212. In other embodiments, thetransducer structure 202 can also include silicon nitride, aluminumnitride (AlN), and/or other suitable intermediate materials.

The first and second semiconductor materials 210 and 212 can be dopedsemiconductor materials. In one embodiment, the first semiconductormaterial 210 can be a P-type semiconductor material (e.g., P—GaN), andthe second semiconductor material 212 can be an N-type semiconductormaterial (e.g., N—GaN). In other embodiments, the first and secondsemiconductor materials 210 and 212 may be reversed. In furtherembodiments, the first and second semiconductor materials 210 and 212can individually include at least one of gallium arsenide (GaAs),aluminum gallium arsenide (AlGaAs), gallium arsenide phosphide (GaAsP),gallium(III) phosphide (GaP), zinc selenide (ZnSe), boron nitride (BN),aluminum gallium nitride (AlGaN), and/or other suitable semiconductormaterials.

The active region 214 between the first and second semiconductormaterials 210 and 212 can include a single quantum well (“SQW”), MQWs,and/or a single grain semiconductor material (e.g., InGaN). In oneembodiment, a single grain semiconductor material, such as InGaN canhave a thickness greater than about 10 nanometers and up to about 500nanometers. In certain embodiments, the active region 214 can include anInGaN SQW, GaN/InGaN MQWs, and/or an InGaN bulk material. In otherembodiments, the active region 214 can include aluminum gallium indiumphosphide (AlGaInP), aluminum gallium indium nitride (AlGaInN), and/orother suitable materials or configurations.

In certain embodiments, at least one of the first semiconductor material210, the active region 214, and the second semiconductor material 212can be formed on the growth substrate 220 via metal organic chemicalvapor deposition (“MOCVD”), molecular beam epitaxy (“MBE”), liquid phaseepitaxy (“LPE”), and/or hydride vapor phase epitaxy (“HVPE”). In otherembodiments, at least a portion of the transducer structure 202 may beformed using other suitable epitaxial growth techniques.

As shown in FIGS. 2A and 2B, a first contact 204 can be formed on thefirst semiconductor material 210. In some embodiments, the first contact204 can extend over a large portion of the underlying firstsemiconductor material 210. In other embodiments, the first contact 204can be formed over a smaller portion of the first semiconductor material210. In certain arrangements, the first contact 204 can be a mirrorand/or made from a reflective contact material, including nickel (Ni),silver (Ag), copper (Cu), aluminum (Al), tungsten (W), and/or otherreflective materials. As illustrated in FIGS. 2A and 2B, the firstcontact 204 can be a continuous overlay of contact material formed overthe first semiconductor material 210; however, in other embodiments, theSST die 200 can include separate reflective elements positioned at thefirst side 201 a and overlaying portions of the first semiconductormaterial 210. During subsequent processing stages, the transducerstructure 202 may be inverted such that the reflective first contact 204can redirect emissions (e.g., light) through the active region 214 andtoward the second side 201 b of the SST die 200 (FIG. 2B). In otherembodiments, the first contact 204 can be made from non-reflectivematerials and/or the SST die 200 may not include reflective elements.The first contact 204 can be formed using chemical vapor deposition(“CVD”), physical vapor deposition (“PVD”), atomic layer deposition(“ALD”), spin coating, patterning, and/or other suitable techniquesknown in the art.

A second contact 206 can include a plurality of buried contact elements215 that extend from the first side 201 a of the SST die 200 to or intothe second semiconductor material 212. Referring to FIG. 2B, the buriedcontact elements 215 can be formed by etching or otherwise forming aplurality of channels or openings 219 in the transducer structure 202that extends from the first side 201 a of the transducer structure 202(e.g., the first contact 204 or the first semiconductor material 210) toor into the second semiconductor material 212. In one embodiment, theopenings 219 can be formed before the first contact 204 is formed on thefirst semiconductor material 210 and can extend to or into a portion ofthe second semiconductor material 212 (as shown in FIG. 2B). In anotherembodiment, the openings 219 may be formed after the first contactmaterial 204 is formed at the first side 201 a of the SST die 200. Theetched sidewalls of the openings 219 can be coated with a dielectricmaterial 218 to electrically insulate a second contact material 216along a path extending through the first contact 204, the firstsemiconductor material 210, and the active region 214. The dielectricmaterial 218 can include silicon dioxide (SiO₂), silicon nitride (SiN),and/or other suitable dielectric materials and can be deposited in theopenings 219 via CVD, PVD, ALD, patterning, and/or other suitabletechniques known in the semiconductor fabrication arts.

In a next process step, the buried contact elements 215 can be formed bydisposing the second contact material 216 in the insulated openings 219to electrically connect with exposed portions of the secondsemiconductor material 212 in the openings 219. The second contactmaterial 216 can include titanium (Ti), aluminum (Al), nickel (Ni),silver (Ag), and/or other suitable conductive materials. The secondcontact material 216 can be deposited using CVD, PVD, ALD, patterning,and/or other known suitable techniques. Accordingly, as shown in FIGS.2A and 2B, both the first and second contacts 204 and 206 areelectrically accessible from the first side 201 a of the SST die 200.

FIGS. 2C and 2D illustrate a stage in the process after a dielectricmaterial 222 (e.g., a passivation material) has been formed over thefirst contact 204. Among other functions, the dielectric material 222 isused to protect the underlying transducer structure 202 (with certainfeatures shown in broken lines in FIG. 2C for clarity) from theenvironment and to prevent shorting the first and second contacts 204,206 to each other. The dielectric material 222 can be the same as ordifferent from the dielectric material 218 in the openings 219. Forexample, the dielectric material 222 can include silicon nitride (SiN),silicon dioxide (SiO₂), polyimide, and/or other suitable insulativematerials. As shown in FIG. 2C, the dielectric material 222 can includeapertures 224 that expose portions of the first contact 204. In theillustrated embodiment, the dielectric material 222 includes arectangular aperture 224 associated with each of the individualjunctions 203 a-203 i. In other embodiments, however, the dielectricmaterial 222 can include more or fewer apertures 224 and/or theapertures 224 can have different shapes (e.g., square, circular,irregular, etc.). The dielectric material 222 can be formed using CVD,PVD, patterning, spin coating, and/or other suitable formation methods.The apertures 224 can be formed by selectively depositing or selectivelyremoving portions of the dielectric material 222. In the illustratedembodiment, the dielectric material 222 is positioned to space theexposed first and second contacts 204 and 206 laterally apart from oneanother, and therefore reduce the likelihood of shorting the contacts toeach other during subsequent processing.

As shown in FIGS. 2C and 2D, the dielectric material 222 does not coverthe buried contact elements 215. In a particular embodiment,interconnects 225 can electrically couple the second contact 206 on ajunction (e.g., junction 203 d) to the first contact 204 via theaperture 224 on an adjacent junction (e.g., junction 203 e) such thatthe junctions (e.g., junctions 203 d and 203 e) are coupled in series.Interconnects 225 can be formed by depositing interconnect lines 226over the dielectric material 222 between the buried contact elements 215and the first contact 204 exposed through the apertures 224. Thedielectric material 222 underlying the interconnect lines 226electrically isolates the first contact 204 from the second contact 206.The interconnect lines 226 can be made from a suitable electricallyconductive material, including those used for the second contactmaterial 216, such as nickel (Ni), silver (Ag), copper (Cu), aluminum(Al), tungsten (W) and/or other suitable conductive materials, and canbe formed using deposition, patterning, and/or other suitable methodsknown in the art.

As shown in FIG. 2C, the SST die 200 includes a first external terminal205 which can be positioned on the junction 203 a. The first externalterminal 205 can be an exposed portion of the first contact 204accessible through the aperture 224 at the junction 203 a. Generally,the first external terminal 205 is associated with a first junction(e.g., junction 203 a) of the plurality of serially coupled junctions(e.g., junctions 203 a-203 i); however, in other embodiments, the firstexternal terminal 205 can be associated with another junction 203 b-203i. Similar to the rectangular apertures 224 associated with each of theother individual junctions 203 b-203 i, the first external terminal 205can be formed via a rectangular aperture 224 in the dielectric material222 exposing the portion of first contact 204. In other embodiments, theaperture 224 can have different shapes (e.g., square, circular,irregular, etc.) to expose the first contact 204 to form the firstexternal terminal 205 on the SST die 200.

Likewise, the SST die 200 includes a second external terminal 207 whichcan be positioned at the junction 203 i and/or another junction that isgenerally at a terminal end of a serially coupled group of junctions203. The second external terminal 207 can be made from a suitableelectrically conductive material, including those used for the secondcontact material 216, such as nickel (Ni), silver (Ag), copper (Cu),aluminum (Al), tungsten (W) and/or other suitable conductive materials.The second external terminal 207 can be electrically coupled to thesecond contact 206 and/or the second semiconductor material 212 of theassociated junction (e.g., junction 203 i). For example, as illustratedin FIG. 2C, the second external terminal 207 can be formed usingdeposition, patterning, and/or other suitable methods known in the artover the dielectric material 222 and electrically connected to thesecond contact 206 of the associated junction (e.g., junction 203 i).

In operation, the first and second terminals 205, 207 can be directlyattached and/or otherwise externally coupled to external devices,components or power sources (e.g., AC or DC power supplies). Theindividual junctions 203 a-203 i are configured to emit light and/orother types of electromagnetic radiation in response to an appliedelectrical voltage. In one example, the SST die 200 can be coupledserially or in parallel with other SST dies in an SST array to achievehigh input voltage in the devices incorporating the SST dies 200,thereby improving device performance.

Optionally, and in another embodiment, the SST die 200 can have a thirdcontact or cross-connection contact 250 (shown in dotted lines atjunction 203 c, for example) electrically coupled to the interconnect225 or interconnect lines 226 at one or more the intermediate junctions(e.g., junctions 203 b-203 h). Cross-connection contacts 250 can be usedto form cross connections with additional dies coupled in an array, suchas an SST array. Cross-connection contacts and cross-connections aredescribed in detail with respect to the solid-state transducers and highvoltage SST arrays described in U.S. patent application Ser. No.13/603,106 (Attorney Docket No. 10829-9078.US00), which is incorporatedherein by reference in its entirety. Accordingly, the cross-connectioncontact 250 electrically coupled to the interconnects 125 betweenjunctions 203 (e.g., between junctions 203 c and 203 d) provide theaccessible electrical connection within high voltage (e.g., multiplejunction) SST dies 200. As such, input voltage provided throughterminals 205, 207 may flow through the serially coupled junctions 203and also between parallel coupled strings (not shown) of SST dies 200 toprovide alternative electrical paths for improving light output andhigher flux delivery. Accordingly, array assemblies (not shown) whichincorporate the SST dies 200 having the cross-connection contacts 250,have provisions to overcome junction failure, providing reducedvariation in bias across individually coupled SST dies 200 in the array.Moreover, the array assemblies can remain in use even after a junctionfailure, providing improved chip performance and reliability, therebyreducing manufacturing costs.

In additional embodiments, the SST die 200 can include multiplecross-connection contacts 250 associated with the multiple interconnects125 for providing additional cross-connections (not shown) between, forexample, parallel-coupled SST dies 200. In such embodiments, arrayassemblies (not shown) incorporating SST dies 200 having one or morecross-connection contacts 250 can be configured to include a pluralityof cross-connections (not shown) electrically coupling interconnects 225of SST dies 200 between strings of dies coupled in parallel, forexample.

In one embodiment, the cross-connection contact 250 is externallyaccessible at the first side 201 a of the SST die 200 and across-connection can be formed by wire bonding and/or direct attachment.In other embodiments, the cross-connection contact 250 can be positionedat the first side 201 a of the SST die 200 with suitable insulating ordielectric materials intervening between the cross-connection contact250 and the underlying first semiconductor material 210 and firstcontact 204. Suitable materials for cross-connection contacts 250 caninclude titanium (Ti), aluminum (Al), nickel (Ni), silver (Ag), and/orother suitable conductive materials. The cross-connection contact 250can also be formed using CVD, PVD, ALD or other suitable techniquesknown in the semiconductor fabrication arts.

FIGS. 2E-2L illustrate stages in the process during which an additionaldielectric portions and conductive material are added to the SST die200. Certain underlying features of the SST die 200 are shown in brokenlines in FIGS. 2E, 2G and 2I for purposes of illustration only. In oneembodiment, an additional dielectric portion 228 can be formed of thesame material as the dielectric material 222, or can be differentmaterial. For example, the additional dielectric portion 228 cancomprise silicon nitride, silicon dioxide, polyimide and/or othersuitable dielectric materials. As shown in FIGS. 2E and 2F, theadditional dielectric portion 228 (e.g., a passivation portion) can beselectively deposited (e.g., via CVD, PVD, or other suitable processes)over portions of the SST die 200 that include the first contacts 204,the second contacts 206, the interconnect lines 226 and theinterconnects 225. In some embodiments, the additional dielectricportion 228 can be pre-formed and positioned over the selectedelectrical contacts and interconnecting portions of the SST die 200. Inthe illustrated embodiment, the additional dielectric portion 228 ispositioned over all of the first contacts 204, the second contacts 206,the interconnect lines 226 and the interconnects 225. Additionally, andas shown in FIG. 2E, the additional dielectric portion 228 ispositioned, deposited, patterned and/or otherwise configured so as notto cover the first and second external terminals 205, 207. In otherembodiments, the SST dies 200 can include larger or smaller regions ofdielectric material and/or portion 222 and 228 that cover larger orsmaller portions of the first and second contacts 204 and 206 and theinterconnects 225. For example, the dielectric material and/or portion222 and 228 can be deposited such that one or more second contacts 206are exposed.

FIGS. 2G and 2H illustrate the addition of barrier material 232, such asa barrier metal, that can be deposited over the dielectric material 222and/or the additional dielectric portion 228 on the first side 201 a ofthe SST die 200. The barrier material 232 can include cobalt, ruthenium,tantalum, tantalum nitride, indium oxide, tungsten nitride, titaniumnitride, tungsten titanium (Wti), and/or other suitable isolativeconductive materials, and can be deposited using CVD, PVD, ALD,patterning, and/or other suitable techniques known in the art.

Referring next to FIGS. 21 and 2J, a metallic seed material 234 can bedeposited over and adhered to the barrier material 232 on the first side201 a of the SST die 200 to provide, for example, a conductiveconnection between the underlying transducer structure 202 and otherexternal components. In the illustrated embodiment, the seed material234 covers the entire first side 201 a. In one embodiment, the seedmaterial 234 can include a thin and continuous overlay, or in otherarrangements, a non-continuous overlay of Copper (Cu), a titanium/copperalloy, and/or other suitable conductive materials, and can be depositedby electroplating, electroless plating, or other methods. For example,the seed material 234 can be deposited using CVD, PVD, ALD, patterning,sputter-depositing and/or other suitable techniques known in the art.

Referring to FIGS. 2G-2J together, the barrier material 232 prevents thediffusion of the seed material 234 (e.g., Cu seed material) fromdiffusing into the underlying semiconductor materials, such as thedielectric material 222, the additional dielectric portion 228, or thetransducer structure 202, including the first and second semiconductormaterials 210, 212 and the active region 214, which could alter theelectrical characteristics of the SST die 200.

FIGS. 21 and 2J also illustrate a stage in the process in which the seedmaterial 234 and the barrier material 232 is patterned to expose theunderlying dielectric material 222 or the additional dielectric portion228. As shown in FIG. 21 , the seed material 234 and barrier material232 can be selectively removed or etched to create a dielectric path 236on the first side 201 a that surrounds and electrically isolates thefirst external terminal 205 and the second external terminal 207. Inanother embodiment the barrier material 232 and/or seed material 234 canbe selectively deposited over the dielectric material 222 and dielectricportion 228 while leaving those sections forming the dielectric path 236void of barrier material 232 and/or seed material 234, respectively.

FIGS. 2K and 2L illustrate a stage in the process in which a metalsubstrate 238 is formed over the seed material 234 on the first side 201a of the SST die 200. In one embodiment, the metal substrate 238 cancomprise copper (Cu), aluminum (Al), an alloy (e.g., a NiFe alloy), orother suitable material. The metal substrate can be formed byelectroplating, electroless plating, or other technique know in the art.In some embodiments, the metal substrate 238 can have a thickness ofapproximately 100 μm; however, in other embodiments, the metal substrate238 can have a variety of thicknesses. As shown in FIGS. 2K and 2L, themetal substrate 238 (e.g., thick copper substrate) can be patterned toexpose the underlying dielectric material 222 or the additionaldielectric portion 228 along the dielectric path 336. In one embodiment,the metal substrate 238 can be selectively plated such that thosesections of the dielectric material 222 and the dielectric portion 228forming the dielectric path 236 is void of the metal substrate 238. Asdescribed, the dielectric path 236 surrounds and electrically isolatesthe first external terminal 205 and the second external terminal 207.The conductive metal substrate 238 electrically and vertically coupledto the first and second external terminals 205, 207 and surrounded bythe dielectric path 236, provides external bonding sites for directattachment of external components without the need for additional wirebonds or bond pads.

Referring back to FIG. 2K, the metal substrate 238 can be thermallyconductive to transfer heat from the SST die 200 to an external heatsink (not shown) and provide the SST die 200 with a thermal pad 240 onthe first side 201 a. For example, the metal substrate 238 can comprisecopper, aluminum or an alloy that has a coefficient of thermal expansionat least generally similar to the coefficient of thermal expansion ofthe SST die 200 or to that of a larger package or circuit board that theSST die 200 is associated. Accordingly, the thermal pad 240 can decreasethe operating temperature of the SST die 200 by transferring heat to aboard, a package, a heat sink, or another element of a device thatincludes the SST die 200. Additionally, although the illustratedembodiment of FIG. 2K includes only one thermal pad 240, in otherembodiments, the SST die 200 may include a plurality of smaller and/orseparate thermal pads 240 having any of a variety of suitable sizes andshapes and located at any of a variety of suitable positions on thefirst side 201 a of the SST die 200.

The SST die 200 (FIG. 2L) can be attached to another carrier substrate(not shown) or otherwise inverted and the metal substrate 238 canprovide a support for further processing on the second side 201 b of theSST die 200. FIGS. 3A-3B are schematic cross-sectional views of the SSTdie 200 of FIG. 2L in various stages of further processing. For example,FIGS. 3A and 3B illustrate a step in the process where the SST die 200has been inverted, and the growth substrate 220 has been removed (FIG.4B), such that the transducer structure 202 is exposed at the secondside 201 b of the SST die 200. The growth substrate 220 can be removedby chemical-mechanical planarization (CMP), backgrinding, etching (e.g.,wet etching, dry etching, etc.), chemical or mechanical lift-off, and/orother removal techniques. The process can also include roughening of thesecond semiconductor material 212 (not shown). Similarly, the metalsubstrate 138 can be ground or thinned, if desired, by backgrinding,CMP, etching, and/or other suitable methods (not shown). In furtherembodiments not shown, the SST die 200 can undergo additional processingto enhance or improve (e.g., optimize) optical properties, and/or otherproperties. For example, optical elements, such as lenses, can be addedto second side 201 b of the SST die 200. The resulting SST die 200includes the first external terminal 205 (shown in FIG. 2K), a secondexternal terminal 207, and the thermal pad 240 (shown in FIG. 2K) at thefirst side 201 a and that can be mounted on a board, a package oranother component without requiring wire bonds e.g., using a solderreflow process. Accordingly, the direct attach terminals 205, 207 andthermal pad 240 allow the SST die 200 to be efficiently mounted to aboard or other substrate or support in a single step process.

For illustrative purposes, FIGS. 2A-3B show stages of a fabricationprocess on an individual SST die 200. FIGS. 4A-4C show portions ofwafer-level assemblies having a plurality of SST dies 200. A personskilled in the art will recognize that each stage of the processesdescribed herein can be performed at the wafer level or at the dielevel. FIG. 4A is a plan view of a portion of a wafer level assembly 400having a first side 401 a and including four individual SST dies 200generally similar to that shown in FIG. 21 . Accordingly, FIG. 4Aillustrates a stage in the process of fabrication in which the metallicseed material 234 is deposited over and adhered to the underlyingbarrier material 232 (shown in FIGS. 2G, 2H and 2J, for example) on thefirst side 401 a of the wafer level assembly 400 to provide, forexample, a conductive connection between the underlying transducerstructures 202 (shown in FIG. 2J) and other external components. Asshown in FIG. 4A, the seed material 234 and the barrier material 232(shown in FIG. 2J) are patterned to expose the underlying dielectricmaterial 222 or the additional dielectric portion 228 and create aplurality of dielectric paths 236.

FIG. 4B is a plan view of the portion of the wafer level assembly 400 ata stage in the process generally similar to that shown in FIG. 2K. Forexample, FIG. 4B illustrates a stage in the process of fabrication inwhich the metal substrate 238 is formed over the seed material 234 onthe first side 401 a of the wafer level assembly 400 and patterned toform the plurality of dielectric paths 236. Each of the individual SSTdies 200 includes a thermal pad 240. As shown in FIG. 4C, the assembly400 can be diced along dicing lanes 402 to form singulated SST dies 200,or in another embodiment, can be processed to form an SST array. Thesingulated SST dies 200 include the first external terminal 205, thesecond external terminal 207 and the thermal pad 240 at the first side201 a, 401 a.

From the foregoing, it will be appreciated that specific embodiments ofthe technology have been described herein for purposes of illustration,but that various modifications may be made without deviating from thedisclosure. The SST dies 200 and the assembly 400 can include additionalcomponents, and/or different combinations of the components describedherein. For example, the SST dies 200 and/or the assembly 400 can beincorporated into SST arrays having multiple dies or assemblies.Further, optical elements, such as lenses can be added to each of theindividual SST dies 200. Furthermore, the assembly 400 includes a 2×2array of SST dies 200, however, in other embodiments, assemblies caninclude different numbers of SST dies and/or have different shapes(e.g., rectangular, circular, etc.). Additionally, certain aspects ofthe present technology described in the context of particularembodiments may be eliminated in other embodiments. For example, theconfiguration of the dielectric material 222 and the dielectric portion228 can be altered to expose or cover differing combinations ofcontacts, interconnects and/or other conductive lines. Additionally,while features associated with certain embodiments of the presenttechnology have been described in the context of those embodiments,other embodiments may also exhibit such features, and not allembodiments need necessarily exhibit such features to fall within thescope of the technology. Accordingly, the disclosure and associatedtechnology can encompass other embodiments not expressly shown ordescribed herein.

We claim:
 1. A solid-state transducer (SST) die, comprising: a firstterminal; a second terminal; a plurality of SST junctions coupled inseries between the first terminal and the second terminal; and a thermalpad vertically aligned with and spaced apart from the plurality of SSTjunctions.
 2. The SST die of claim 1, wherein the plurality of SSTjunctions are coupled in series by a corresponding plurality ofinterconnects.
 3. The SST die of claim 1, wherein the thermal pad iselectrically isolated from the plurality of SST junctions by adielectric material covering contacts of the plurality of SST junctions.4. The SST die of claim 3, wherein the dielectric material comprisessilicon nitride (SiN), silicon dioxide (SiO2), polyimide, or acombination thereof.
 5. The SST die of claim 3, further comprising aseed material between the dielectric material and the thermal pad. 6.The SST die of claim 5, wherein the seed material comprises copper (Cu),titanium (Ti) or an alloy thereof.
 7. The SST die of claim 1, furthercomprising an insulating material disposed between adjacent ones of theplurality of SST junctions.
 8. The SST die of claim 1, wherein the firstterminal and the second terminal are co-planar with the thermal pad. 9.The SST die of claim 1, wherein each of the plurality of SST junctionscomprises a first semiconductor material, a second semiconductormaterial, and a light-emitting active region between the firstsemiconductor material and the second semiconductor material.
 10. TheSST die of claim 1, wherein the thermal pad, the first terminal, and thesecond terminal are all comprised by a metal substrate.
 11. The SST dieof claim 10, wherein the metal substrate comprises copper (Cu), aluminum(Al), or a nickel iron (NiFe) alloy.
 12. The SST die of claim 10,wherein the metal substrate has a first coefficient of thermal expansionabout equal to a second coefficient of thermal expansion of the SST die.13. A solid-state transducer (SST) die, comprising: a plurality of SSTjunctions coupled in series; a metal substrate carrying the plurality ofSST junctions, the metal substrate comprising a thermal pad; and adielectric material spacing the metal substrate from the plurality ofSST junctions.
 14. The SST die of claim 13, wherein the metal substratefurther comprises a first terminal and a second terminal that areelectrically isolated from the thermal pad.
 15. The SST die of claim 14,wherein the plurality of SST junctions are coupled in series between thefirst terminal and the second terminal.
 16. The SST die of claim 14,wherein the thermal pad, the first terminal, and the second terminal areelectrically isolated from each other by openings in the metal substrateexposing the dielectric material.
 17. The SST die of claim 13, whereinthe metal substrate has a first coefficient of thermal expansion aboutequal to a second coefficient of thermal expansion of the SST die. 18.The SST die of claim 13, wherein the metal substrate comprises copper(Cu), aluminum (Al), or a nickel iron (NiFe) alloy.
 19. The SST die ofclaim 13, wherein the dielectric material comprises silicon nitride(SiN), silicon dioxide (SiO2), polyimide, or a combination thereof. 20.A solid-state transducer (SST) die, comprising: a plurality of SSTjunctions coupled in series; a metal substrate having a firstcoefficient of thermal expansion about equal to a second coefficient ofthermal expansion of the SST die; and a dielectric material spacing theplurality of SST junctions from the metal substrate.